Cooperative External Acidity and Surface Barriers of HZSM-5 in the Coupling Reaction of CH3Cl and CO to Aromatics

The acidity and diffusion barriers of zeolites, especially the external surface, are prevailing parameters in the zeolite-catalyzed synthesis of aromatics. Nonetheless, how to well coordinate the external acidity and surface barriers to obtain high benzene-toluene-xylene (BTX) selectivity and exceptional stability remains a great challenge. Herein, we experimentally demonstrate the synergistic effect of external acidity and surface barriers in the coupling of CH3Cl and CO to aromatics via a surface modification strategy. The results manifest that product selectivity is controlled by external acidity, while catalyst lifetime is controlled by surface barriers. Accordingly, when simultaneously passivating the external acidic sites and reducing the surface barriers, the BTX selectivity was enhanced by 133%, and the catalyst lifetime was prolonged. Our findings provide a new perspective for rational designing of catalysts with superior performance based on controlling the acidity and mass transfer on purpose.

Automated summary

This study experimentally demonstrates the synergistic effect of external acidity and surface barriers in the catalytic synthesis of aromatics. The selectivity of products is controlled by external acidity, while the lifetime of the catalyst is controlled by surface barriers. By simultaneously passivating the external acidic sites and reducing the surface barriers, the BTX selectivity was enhanced by 133% and the catalyst lifetime was prolonged.